Efectos del carbonato y bicarbonato en la resistencia a la corrosión en aceros API 5L con tratamientos térmicos de recocido, normalizado y bonificado

Abstract

This document analyzes the effects of carbonates and bicarbonates on corrosion resistance for API 5L X42 and Grade B steels, due to the corrosive action of CO2 condensation when mixed with liquid water or steam. These steels were subjected to heat treatments of Annealed, normalized and tempered, it was compared between these and the supply material in order to find microstructural differences, as well as the formation of carbonates or bicarbonates on the surface tested by means of SEM. Vickers Hardness tests were carried out under NTE INEN ISO 6507-1 and impact under the ASTM E23 standard, as well as corrosion tests, performing a CO2 saturation for 1 hour at 99.9%, an electrolyte under the ASTM D-1141 standard, using a Metrohm Autolab electrochemical cell with a 1L capacity under the ASTM standard G5, a Potentiostat / Galvanostat PGSTAT204 Metrohm Autolab, lastly for the analysis the NOVA 2.1 Software was used. From these tests, as expected when performing a heat treatment, the hardness, and the ability to absorb energy during an impact vary for all heat treatments with respect to the supply material. In addition, it was determined that the standardized API 5L X42 steel presents a Considerable 2.54% improvement in corrosion resistance over supply; API 5L Grade B steel improves by 46.47% compared to normalized. In conclusion, the hardened API 5L Grade B steel is the one with the best corrosion resistance due to the formation of Calcium Carbonates and Iron Carbonates, verified by means of an EDS, a thin layer of carbonates is formed on the surface of the materials. It is recommended the creation of new branches of research where the temperature and the electrolyte are different to relate them and get new conclusions.